MMAN Statistics

Some background on memory broker:

The Automatic Shared Memory Management feature uses background process named Memory Manager (MMAN).MMAN serves as the SGA Memory Broker and coordinates the sizing of the memory components. The SGA Memory Broker keeps track of the sizes of the components and pending resize operations.There is not so many document on this process but here is some help:

Let’s see what is MMAN responsible for :
SQL> select substr(DEST,1,10) DEST, DESCRIPTION from x$messages where DEST=’MMAN’;

DEST DESCRIPTION
—————————— ——————————————————–
MMAN lock memory at startup
MMAN lock memory timeout action
MMAN Memory Management
MMAN Complete deferred initialization of components
MMAN Handle sga_target resize
MMAN Handle mem_target resize
MMAN Handle sga_target deferred request delete
MMAN Reset advisory pool when advisory turned ON

The SGA Memory Broker keeps track of the sizes of the components and pending resize operations.

We can dump memory broker statistics into trace file using

oradebug dump DUMP_ADV_SNAPSHOTS command e.g.
SQL> oradebug setmypid
SQL> oradebug dump DUMP_ADV_SNAPSHOTS 0

Default value for memory broker statistis is 30 sec.It is controled by underscore parameter

_memory_broker_stat_interval 30 memory broker statistics gathering interval for auto sga

and can be changed with alter system command e.g.

alter system set “_memory_broker_stat_interval”=60 scope=both sid=’demo1′; will change gathering interval to one minute.

New snapshot will be generated after _memory_broker_stat_interval expires.

Trace file has various statistics for diffrent SGA components.Note snapshots numbers and timestamp.

Processing Oradebug command ‘dump DUMP_ADV_SNAPSHOTS 0′
Dumping memory broker statistics snapshots 5677
0: ———————————————————–
Stats Entry #5646 taken at timestamp 671200759
Stat Value
——————————-
DB time 355973
DEFAULT cache read count 33608
DEFAULT cache read time 227
shared pool load count 24336
shared pool load time 53486
java pool load count 422
java pool load time 11
shared io pool wait time 0
Component Granules
——————————-
DEFAULT cache 70
Shared Pool 33
Large Pool 1
Java Pool 2
SGA Target 107
PGA Target 72
Default Cache Advice Version=12 Start Index of Version=9
Default Cache Granules -> Estimated Read Time
———————————————–
———————————————–
7 -> 364, 14 -> 275, 21 -> 235, 28 -> 227, 35 -> 227, 42 -> 227, 49 -> 227, 56 -> 227, 63 -> 227, 70 -> 227, 77 -> 227, 84 -> 227, 91 -> 227, 98
-> 227, 105 -> 227, 112 -> 227, 119 -> 227, 126 -> 227, 133 -> 227, 140 -> 227
Shared Pool Advice Version=16 Start Index of Version=9
Shared Pool Granules -> Estimated Load Time
———————————————–
25 -> 3590, 29 -> 1856, 33 -> 195, 37 -> 1, 41 -> 1, 45 -> 1, 49 -> 1, 53 -> 1, 57 -> 1, 61 -> 1, 65 -> 1, 69 -> 1
Java Pool Advice Version=2 Start Index of Version=20
Java Pool Granules -> Estimated Load Time
———————————————–
1 -> 195, 2 -> 195, 3 -> 195, 4 -> 195
PGA Target Advice Version=1 Start Index of Version=0
PGA Granules -> Estimated PGA Processing Time
———————————————–
9 -> 11962649, 18 -> 11886641, 36 -> 11886641, 54 -> 11886641, 72 -> 11886641, 86 -> 11886641, 100 -> 11886641, 115 -> 11886641, 129 -> 11886641,
144 -> 11886641, 216 -> 11886641, 288 -> 11886641, 432 -> 11886641, 576 -> 11886641
————————————————————-
1: ———————————————————–
Stats Entry #5677 taken at timestamp 671202561